1. Field of the Invention
The present invention relates to a heat dissipating fan and, more particularly, to a heat dissipating fan that can easily be processed, manufactured, and assembled.
2. Description of the Related Art
FIG. 1 shows a conventional heat dissipating fan 80 including a housing 81, a stator 82, a rotor 83, a driving device 84, and an impeller 85. The housing 81 consists of first and second housing parts 811 and 812 fixed together by fasteners 813 such as screws or rivets. The stator 82 includes a magnetically conductive element 821. The rotor 83 includes a shaft 831 and a magnetic element 832. The shaft 831 extends through the housing 81 and is rotatably supported by first and second bearings 833 and 834. The magnetic element 832 is mounted around the shaft 831 and aligned with the magnetically conductive element 821. The driving device 84 is electrically connected to the magnetically conductive element 821. The impeller 85 is coupled to the shaft 831 and located outside of the housing 81. The driving device 84 can control the direction of electric current of the magnetically conductive element 821 to magnetically interact with the magnetic element 832 for driving the rotor 83 and the impeller 85 to rotate. An example of such a heat dissipating fan is disclosed in Taiwan Patent Publication No. 200744290. However, the heat dissipating fan 80 does not include an outer casing, such that the air currents generated by rotation of the impeller 85 can not be effectively guided to the heat generating portion of the electronic product and fails to provide satisfactory heat dissipating effect.
FIG. 2 shows another conventional heat dissipating fan 90 including a housing 91, a motor 92, an impeller 93, and a circuit board 94. The housing 91 includes a housing portion 911 and a motor casing 912 that are formed of plastic material by injection molding. The motor casing 912 is located in the housing portion 911 and interconnected by connecting members 913 in the form of ribs to the housing 911. The motor 92 is mounted in the motor casing 912 and includes a shaft 921, a magnetic element 922, and a stator 923. The shaft 921 is rotatably supported by two bearings 924 and has an end extending beyond the motor casing 912. The magnetic element 922 is mounted to the shaft 921 and aligned with the stator 923. The impeller 93 is mounted to the end of the shaft 921 and located outside of the motor casing 912. The circuit board 94 is electrically connected to the stator 923. The motor 92 can drive the impeller 93 to rotate for providing heat dissipating functions. The housing 91 formed by injection molding guides the air currents generated by rotation of the impeller 93. However, the motor casing 912 of the housing 91 made of plastic material can not provide a magnetically sealing function while the stator 923 magnetically interacts with the magnetic element 922 under control of the circuit board 94. Thus, magnetic leakage is liable to occur, and electromagnetic interference occurs, leading to adverse affect to the operational effect of the impeller 93 and to the heat dissipating effect of the heat dissipating fan 90. Furthermore, it is difficult to install the magnetic element 922, the stator 923, and the circuit board 94 in the housing portion 911 and the motor casing 912, particularly when the housing 91, the motor 92, and the impeller 93 are of larger sizes. Further, it is difficult and expensive to manufacture a metal housing 91 of a larger size.